U.S. Pat. No. 5,712,934, issued Jan. 27, 1998, describes a “Fiber Optic Infrared Sensor” to detect the presence of water (as compared to air) or another fluid having a refractive index substantially greater than air. Such system uses a return bent optical fiber. Light is transmitted into one end of the fiber, and a photosensitive component provides a measure of the intensity of light leaving the other end. As described in such patent, the intensity of light sensed at the output end provides an indication of the presence of water or another fluid at the bend of the fiber. This technology has been in use in the “EOS” (environmental optical sensor) product available from Cambria Corporation of Seattle, Wash. Other fiber optic sensing systems are described and cited in U.S. Pat. No. 5,712,934.